You don’t. HRMs just guess really. I think you need a lab and exercise bike…?

In fairness i’m not really looking for lab type accuracy, just a fair idea, clearly online sites are nonsense, is a heart rate monitors guess a half decent guess? i’m not really after more than that..I’m not an athlete and never will be, just looking for a way to gage my activities as i try to improve, distance and elevation are a couple things i’m looking to keep track of, calories burnt is another i’m thinking of..

If you use the same device over several rides, the numbers will be comparable. So if you get 600 on one ride, then 700 on the next, you can be sure that second ride burned about 15% more calories. Whether the absolute numbers are ‘correct’ is pretty difficult to know, but as a tool for comparison it is reasonably useful.

I really don’t think so. There are so many variables. Your heart rate vs power developed varies during a ride anyway (cardiac drift), and it varies day to day with things like illness and condition. I find that if I ride hard one day then ride again the following day my heart rate for a given power is 10bpm or more lower. Don’t ask me why!

My guess is that the Polar ones are a bit better since they at least do some kind of test on you before calculating.

i burn fat easier onroad than off, based on no HRM use, just hours on the bike and bathroom scales, but I feel like i work as hard overall on either bike. I think on the road it’s easier to settle into a rhythm and you burn fat at this pace, plus the efforts can be more sustained; off-road is more interval-like and that uses up glycogen and o2 more, good for spring fitness. I read somewhere that a strong coffee, a hard hill effort at max or two, then a steady mid-pace ride burns fat effectively and you can dothat on or off-road.

i get fit more effectively on-road too, more leg/lungwork and less tech per hours on the bike. actual calories used, not sure how it varies, i just try to balance calories in and calories out overall. maybe 500 an hour on a brisk ride for an average 12-13st rider at an average 8-10mph off-road / 17-18mph onroad?